The incidence of endometrial cancer in Northern California Caucasian women has been rising steadily over the last decade or so, at a rate considerably greater than chance expectancy. Suspect as causative agents of this rising trend are hormonal influences from prior reproductive experiences and exogenous female hormones taken therapeutically. Using epidemiologic methods of case-control design, we intend to study the childbearing practices (e.g. age at first birth, child spacing, number of children, infertility, etc.), together with the use of post-menopausal and other hormones, of women who develop endometrial cancer and of appropriate control women who do not. Information will be collected by hospital or home interviews with study subjects living in five San Francisco Bay Area counties. We anticipate being able to identify the kinds of pregnancy and childbearing experiences that identify those women who are at greatest risk of subsequent endometrial cancer. Relative risks of endometrial cancer will be computed for women who chose to remain childless, for those who deliberately decided on late parity, and for those who were unable to conceive.